The prior art provides a number of mechanisms for implanting materials, particularly medically applicable materials, in an animal. U.S. Pat. No. 4,451,253 (Harman) teaches an implant injector with a stable obturator held secured within the injector body and a retractable, hollow needle or trocar. In its initial position the needle is extended such that an implant rests inside the needle against the distal end of the stable obturator. After the needle is injected into the desired position, the retractable needle is withdrawn along the obturator to uncover and deposit the implant. U.S. Pat. No. 4,820,267 (Harman), U.S. Pat. No. 4,846,793 (Leonard et al.) and U.S. Pat. No. 4,994,028 (Leonard et al.) disclose devices with hollow, needle-like cannulas for implantation of a plurality of solid, elongated medicinal pellets. These devices are designed such that a user slides a manually engageable knob along the body of the instrument to move a plunger through the needle and dispense the pellets. U.S. Pat. No. 4,661,103 (Harman) teaches a similar device with a slotted barrel element to slidably mount an integral magazine for multiple implant pellets. U.S. Pat. No. 4,871,094 (Gall et al.) provides an implantation device which utilizes a syringe-like, distally-protruding coaxial plunger and a side-loading opening for placing implants in the injector. The Gall et al. devices also include a staggered channel passing through the external surface of the device's body, with each section of the channel corresponding roughly in length to that of the implants. A laterally protruding knob on the plunger slides between points within the staggered channel to facilitate implantation of one pellet at a time. U.S. Pat. No. 4,900,304 (Fujioka et al.) teaches another standard plunger, side-loading implantation device. The Fujioka et al. device differs in its side-loading activity from that seen in the Gall et al. device, above, in that the loading port is located in the side of the device's needle or trocar member, which is loaded with implants prior to being inserted into the body of the injector. U.S. Pat. No. 4,402,308 (Scott) describes an implant injector having a hollow, slotted needle or trocar rotatably mounted inside a sheath, the sheath being retractable to expose any portion of the slotted needle. U.S. Pat. No. 4,941,874 (Sandow et al.) provides for a transparent implantation device with a protective covering to protect the plunger rod and prevent it from falling out. U.S. Pat. No. 4,753,636 (Free) teaches a syringe-style implant injector in which a tab-like clip is releasably secured to positions on the obturator to regulate its forward progress and limit each implantation to a single implant pellet. U.S. Pat. No. 4,147,164 (Behney) directs a method of placing shape correcting implants into canine ears. Finally, U.S. Pat. No. 5,385,554 (Brimhall) teaches a wing-shaped pair of extensions for a catheter inducer which facilitates the gripping of the needle.
In addition, the prior art has addressed some means and methods for inserting devices into tissues at reasonably prescribed angles. U.S. Pat. No. 2,577,481 (Piechaczek) set forth an apparatus comprising, generally, a flattened base to be placed against a patient's skin and adjustable means for altering the angle at which a hypodermic needle passes through the plane of the base. Similarly, U.S. Pat. Nos. 5,024,665 and 4,966,589 (both to Kaufman) describes a composite catheter assembly which secures the body and needle of an inserting device such that its angle of penetration into the body is substantially maintained during operation. U.S. Pat. No. 5,192,271 (Kalb et al.) discloses a device for delivering an injection to a penis, the device comprising a ring designed to encircle the penis, the ring having one or more tubular extensions protruding from the ring such that a hypodermic needle passing through the tube and ring is guided to the central erectile tissue. U.S. Pat. No. 5,395,317 (Kambin) provides a method of treating a herniated disc, the method including a jig which utilizes substantially parallel channels in a jig and an original guide passing through one channel to align subsequent linear devices and direct them toward the desired location in relation to the disc. U.S. Pat. No. 4,403,987 (Gottinger) discloses an injection aid comprising, in general terms, a hypodermic syringe, an angled ramp means, and a slidable base, the base being designed to secure the syringe and slide down the ramp means at the prescribed angle to make a desired injection into a limb.U.S. Pat. No. 3,324,854 (Reese) and U.S. Pat. No.2,660,169 (Malm) disclose syringe attachments which protrude from the needle end of a syringe and allow the user to guide the syringe's needle into a specified, upraised portion of skin. Finally, U.S. Pat. No. 5,300,079 (Niezink et al.) teaches a spring operated injector designed to implant objects such as transponders used for identifying hogs. The injector utilizes a positioning means comprising a pin which is set against a body as a guide for an insertion needle to be passed parallel to the pin and into and out of the body.
While the devices of the prior art provide means for inserting a solid subcutaneous implant into a patient or certain means for determining the angle at which an injection or implantation is made, none limits the angle of insertion such that the device or materials they are designed to implant can be placed only at the desired depth underneath and substantially parallel to the surface of the tissue.